1. Field of the Invention
This invention relates in general to certain new and useful improvements in reinforced plastic composite articles which may have non-constant cross-sectional shapes over their length and an apparatus and method for producing the same and more particularly, to reinforced plastic composite articles and an apparatus and method for producing the same, such that the reinforced plastic composite articles have a first portion of a cross-sectional shape which is different than the cross-sectional shape of an integral second portion of the same article over the length thereof, or otherwise articles which have a different cross-sectional volume over their length.
2. Brief Description of the Prior Art
For several years, various forms of reinforced plastic articles, generally structural articles, have been produced by the technique of pultrusion and include a wide variety of bars, tubes and other profile forms. These articles have found widespread use in widely diversified fields of application, including, for example, electrical, industrial, and structural applications, and even in consumer end products. In fact, due to the relatively low cost of reinforced plastic composite articles, the corrosion resistance attributes, and the very substantial strength-weight ratio afforded by these articles, in many cases they have replaced counterpart articles typically constructed from metals and other materials.
The pultrusion method and apparatus generally involves the straight pulling of various types of continuous composite reinforcements, such as continuous glass, graphite, or boron, through a resin impregnation system and through a shaping and forming die where the composite composition is cured into its final structural form. In this system, the shaping and forming die, which is linear over its length, generally imparts to the composite, the size and shape of the die and the composite is then cured in this final size and shape as it exits the shaping and forming die. This type of pultrusion system is more fully illustrated and described in U.S. Pat. No. 2,871,911, dated Feb. 3, 1959 and in U.S. Pat. No. 3,556,888, dated Jan. 19, 1971 by William Brandt Goldsworthy.
The conventional pultrusion system is somewhat analogous to extrusion, in that the pultrusion system operates continuously to produce constant-section shapes and profiles, which may be formed of a resin matrix impregnated reinforcing fiberous material such as, for example, fibrous-glass and polyester resin. In this type of pultrusion system, the composite article is essentially pulled through the shaping/forming die in a substantially linear path, by means of one or more puller mechanisms, which are located downstream from the shaping/forming die. In this way, the composite article is formed on a continuous basis as a linear profile form.
For many years, only relatively straight pultruded articles could be formed. U.S. Pat. No. 3,873,399, dated Mar. 25, 1975 by William Brandt Goldsworthy, et al., provided a method and an apparatus whereby reinforced plastic composite articles could be curved over at least a portion of their length. In accordance with this apparatus and method, a moving die which generally rotated in an arcuate path and having a die channel cooperated with a stationary die such that the combination of the mating two dies could form a die channel. As the moveable die was rotated, reinforced plastic composite materials were pulled through the die channel and simultaneously cured while in the die channel in order to form an article which was curved over a portion of its length.
In the aforesaid U.S. Pat. No. 3,873,399, there is also taught a method of producing articles which were curved, but did not have a constant radius. In other words, one portion of an article, which was arcuate in shape, was defined by a radius which was different from another portion of the same integrally formed article. However, in order to produce such an article, a very cumbersome and time consuming manual intervention was required. For example, in order to form two arcuately shaped legs connected by a corner portion, it was necessary to form the first arcuately shaped leg, remove the die, thereafter manually bend the corner portion, and subsequently with another die, form the second arcuately shaped leg. Thus, the apparatus, while capable of producing such an article, was very cumbersome and not very effective in this particular aspect.
Also, in the aforesaid U.S. Pat. No. 3,873,399, there is taught an apparatus and method for producing an article which was referred to as being of non-constant cross-sectional shape. In the context of the aforesaid U.S. Pat. No. 3,873,399, an article having non-constant cross-sectional shape was one that had a different shape at an upper portion, for example, compared to a lower portion. In other words, a T-shaped article could be produced so that the upper section had a generally horizontally disposed segment and the lower section had a generally vertically disposed segment. Nevertheless, the articles which were produced in accordance with the apparatus and method taught in the aforesaid U.S. Pat. No. 3,873,399 always had a constant cross-sectional shape over their length. In other words, one portion of the article could not have been produced with a cross-sectional shape different than another integral portion of the same article.